KQ,"
Occurrence of Chlorinated Polynuclear Aromatic Hydrocarbons in Tap Water Hiroaki Shiraishl,* Norman H. Pilkington,+Aklra Otsukl, and Kelichlro Fuwa
Division of Chemistry and Physics, National Institute for Environmental Studles, Yatabe, Tsukuba, Ibaraki 305,Japan I Organic compounds in tap waters were extracted by a
modified continuous liquid-liquid extractor and analyzed by computerized gas chromatography/mass spectrometry using a fused silica capillary column. The results indicate the presence of momochlorinated derivatives of naphthalene, dibenzofuran, fluorene, fluorenone, phenanthrene, and fluoranthene and dichlorinated derivatives of naphthalene, phenanthrene, and fluoranthene. The parent polynuclear aromatic hydrocarbons (PAHs) and their oxygenated derivatives such as fluorenone and anthraquinone were also found. I t was demonstrated that chlorinated PAHs (Cl-PAHs) were reaIly present in tap waters a t W-W ng/L levels. The use of chlorine for disinfection of public water supplies has been shown to form halogenated organic compounds, such as trihalomethanes, and "nonvolatile" mutagens ( I ) , but the identity and extent of halogenated compounds in drinking water are still unknown. Among the numerous organic compounds identified in tap water samples, the presence of polynuclear aromatic hydrocarbons (PAHs) has been reported (2-7). Laboratory studies using pure standards have shown (8-11) that both oxygenated and chlorinated derivatives can be formed during chlorination of PAHs in dilute aqueous solutions. It was therefore suspected that such compounds might also be present in tap waters. Because of the low concentration of organic compounds in tap water, preconcentration was required before the analysis of these compounds by gas chromatography/mass spectrometry (GC/MS). An attempt to analyze PAHs in water by a closed loop stripping method (12) failed, because elution of PAHs from the carbon filter was difficult. A continuous liquid-liquid extraction method (13-15), often used in pesticide analysis, can both conveniently handle several hundred liters of water and also provide an extremely low reagent blank, because it requires only 100 or 200 mL of organic solvent. For the present work, such a continuous liquid-liquid extractor was used, with some modifications, to extract nonpolar organic compounds in tap water. The concentrates were analyzed by GC/MS using a fused silica capillary column.
Experimental Section Materials. The hexane was pesticide grade (Wako Pure Chemicals Ind., Ltd) and required no further purification Permanent address: CSIRO Division of Chemical and Wood Technology, Clayton, Victoria 3168, Australia. 0013-936X/85/0919-0585$01.50/0
before use. Water was purified by distillation, and passage through the Milli-Q system (Millipore Corp.) and XAD-2 resin column before use. Chlorinated PAHs (Cl-PAHs) for use as reference standards were prepared by chlorination of the parent PAH. PAH (0.1 g) was dissolved in 10 mL of acetic acid, and 1.5 times the stoichiometric amount of 10% sodium hypochlorite solution was added dropwise into this solution while stirring. After the mixture had been stirred for 3 h, water and ether were added. The organic layer was washed with water and then with sodium carbonate solution and dried over sodium sulfate. Ether was removed by distillation, and the residual solid was purified by vacuum distillation (or sublimation) and recrystallization from methanol. Modification of Extractor. As reported by Stachel et al. (15)the decrease in water level which occurred during extraction made operation of the Ahnoff and Josefsson extractor (19) difficult. In order to overcome this undesirable phenomenon, the continuous liquid-liquid extractor (see Figure 1) was modified to regulate the water level. A commercial automatic water level controller (Nissin Rika Co., Model AL-66r) operating in on-off delay mode was used. The water level is monitored by an infrared sensor on the side arm of the extractor. If the water level sinks down, air is pumped out through a one-way glass valve, thus causing a partial vacuum inside the extractor. The flow rate of water into the extractor then increases. The pumping speed and delay time were adjusted so as to prevent chattering of the water level. In order to make it easy to change the head of the extractor, a transparent glass joint was adopted instead of the stainless steel flange originally used (19). Apparatus. Mass spectrometry was performed on a DX-300 double-focusing mass spectrometer (JEOL, Japan) fitted with a Hewlett-Packard Model 5700 GC. A flexible capillary column (25 m), methyl silicone (Hewlett-Packard), used with helium as the carrier gas, was directly coupled to the mass spectrometer. The column temperature was set a t 40 "C for 4 min followed by an increase to 250 "C at a rate of 4 "C/min and then held a t 250 "C. The injector temperature was 250 "C, and the head pressure of the column was 1.0 kg/cm2. The mass spectrometric conditions were as follows: accelerating voltage 3 kV; ionizing current 300 PA; ionizing voltage 70 V; scan range m / z 10-400; scan interval 2 s. Mass resolution was 500. A JMS-3500 mass data analysis system (JEOL, Japan) was used. Extraction Procedure. Hexane (0.15 L) was charged to the extractor, and 200 L of tap water (Tsukuba, Japan)
0 1985 American Chemical Society
Environ. Sci. Technoi., Vol. 19, No. 7, 1985
585
Flgue 2. Sampling sites and htap water supply system in Tsukuba. (1) Institute: (2) Branch of Institute.
WATER IN
CONTROLLER
WHP
Flgure 1. Modified liquid-liquid extractor.
was passed through a t a flow rate of 50-60 mL/min. Recovery of hexane was about 0.14 L (more than 94%). The hexane extract was dried by sodium sulfate (5-10 g) and concentrated to a few milliliters on a rotary evaporator and finally to 0.10 mL under a nitrogen stream a t room temperature. Recovery Test. The extractor was fitted with a small reservoir and a Hershherg type dropping funnel. Water (100 mL) was poured into the funnel, and then 5 pL of a standard methanol solution (0.5 mg/mL) of PAHs and CI-PAHs was added to the water. This solution was dynamically diluted by adding it dropwise to a glass reservoir through which water was flowing at 55 m l j m i n . The dilution factor in the cell was 250, so that the net concentration flowing through extractor was 100 ng/L per component. The total volume of water extracted was 25 L, and 150 mL of hexane was used. At first, hexane was concentrated to 1.0 mL and finally to 0.10 mL as described 586
Environ. Sci. Technol.. Vol. 19, No. 7, 1985
above. Recoveries were determined on each evaporation step using 1-chlorodecane and 1-chlorotetradecane as internal standards. Compound Identification and Quantification. The occurrence of mono- and dichlorinated PAH derivatives was confirmed by comparison of its mass spectrum and GC retention time with those from the authentic standards. In cases when the authentic standard was not available, identifications were done by comparison with reported mass spectrum (I6,4). CI-PAHs and PAHs were quantified from the peak area of mass chromatograms using an external standard technique. Molecular ion, M+, and its isotope ion, (M + 2)+, were selected for CI-PAHs, and the diagnostic ion for PAH was its molecular ion. Reproducibility for the determination of CI-PAHs and PAHs by external standard technique was within 12% (calculated from the recovery experiments), so the precision of tap water analyses was dependent upon this final determination step. The detection limits for PAHs and C1-PAHs were 0.01 ng. Therefore, if recovery is 80% and 200 L of sample water is concentrated to 0.10 mL, CI-PAHs and PAHs at 0.003 ng/L can he detected by GC/MS using 2 r L of concentrates, unless coeluting substances interfere with the determination. As low as 0.1 ng of PAHs and CI-PAH could be detected by RIC (reconstructed ion chromatogram), which was used for monitoring GC elution. Sampling. Figure 2 shows the sampling sites and the tap water supply system in Tsukuha. Tap water was sampled in our Institute (site 1) from Dec 1982 to Feb 1984. Two tap water sources were chosen. Tap a was in a 10-year-old building and tap b was in a new building (1 year old). The treatment process used to produce the tap water is as follows. Lake water is pumped to the treatment plant, where chlorination, rapid sand filtration, and activated carbon treatment are carried out. The fmished water is chlorinated to 0.7 mg/L free chlorine, then pumped to Tsukuha, and stored in a plastic tank, where a further 0.3 mgjL chlorine is added. Sometimes well water is blended in, but its ratio to lake water is below 10%. Raw lake water was collected at site 2, where a branch of our Institute is located. Rapid sand filtration was performed before extractions after the model of the procegs a t the water treatment plant.
Results and Discussion Table I shows the result of recovery experiments of some PAHs and CI-PAHs using the extractor. It seems that recovery increases with increase in molecular weight. I t was considered that this may he due to a decrease in their solubility in water, because published values for the solu-
Table I. Recovery (%) of PAHs and Cl-PAHs at 100 ng/L each recovery" f SDb 84 f 1 89 f 4 92 f 4 89 f 4 85 f 5 85 f 4 92 f 4 88 f 2 85 f 5 88 f 2 87 f 1 84 3 85 f 3 85 f 3 80 f 5 81 f 4
naphthalene acenaphthylene acenaphthene dibenzofuran fluorene fluorenone anthracene phenanthrene fluoranthene chloronaphthalene chlorodibenzofuran chlorofluorene chlorofluorenone chlorophenanthrene dichlorophenanthrene chlorofluoranthene final volume, mL
*
1.0
a Means of three independent experiments. deviation.
74 f 1 79 f 4 81 4 79 f 4 77 f 5 80 f 5 90 f 4 83 f 4 84 4 81 f 2 78 i 2 76 f 3 78 f 5 83 f 4 80 f 5 81 f 5
I
*
I
Figure 3. Reconstructed ion chromatogram of the hexane extract (tap a, 83/June, 13-16, 1983). (Peak numbers refer to table 11.)
until the volume of hexane became 1.0 mL, but some of the PAHs were evaporated during further concentration. I t was very important that more than 3 mL of hexane remained in a flask when the rotary evaporator was used. Otherwise, considerable amounts of the PAHs which are more volatile than fluorene were lost. Figure 3 shows reconstructed ion chromatogram (RIC) of the Tsukuba tap water extract (tap a; June 13-16,1983), and Table I1 lists the compounds identified. Dibutyl and
0.10 SD = standard
bility of naphthalene, fluorene, phenanthrene, and fluoranthene are 31.7, 1.98, 1.29, and 0.26 mg/L, respectively (17). But, it was found that the loss of PAHs occurred in the evaporation step. Volatilization of PAHs was negligible Table 11. Identified Compounds in the Tap Water no.
retention time
6 min 24 s 6 min 44 s 6 min 54 s 7 rnin 24 s 8 min 26 s 8 min 46 s 9 min 50 s 8 10 min 28 s 9 11 min 04 s 10 11 min 30 s 11 12 min 06 s 12 12 min 22 s 1 2 3 4 5 6 7
13 min 36 s 14 min 02 s 14 min 38 s 16 rnin 54 s 17 min 54 s 18 min 06 s 18 rnin 16 s
13 14 15 16 17 18 19
19 min 58 s 20 min 14 s 20 min 54 s 22 min 20 s 25 min 12 s 25 min 18 s 26 min 58 s 28 min 22 s 28 28 min 50 s 29 29 min 06 s
20 21 22 23 24 25 26 27
30 29 min 52 s 31 30 rnin 14 s 32 30 min 58 s 33
31 rnin 04 s
34 35
31 min48s 33 min 04 s
identificationa no.
name ethylbenzene p - and m-xylend bromoform o-xylene isopropylbenzene 1-bromohexane propylbenzene ethyltoluene, isomer ethyltoluene, isomer p-dichlorobenzene trimethylbenzene, isomer o-dichlorobenzene unknown compound chloroxylene, isomer hexachloroethane chloroxylene, isomer bromoxylene, isomer hexyl ether, isomer hexyl ether, isomer naphthalene hexyl ether isomer hexyl ether, isomer hexyl ether, isomer 1-bromodecane Di-n-hexyl ether 1-chloronaphthalene biphenyl tetradecane 2,6-di-tert-butylquinone methylbiphenyl , isomer methylbiphenyl, isomer, chloromethylnaphthalene dibenzofuran pentadecane dichloronaphthalene, isomer dichloronaphthalene, isomer fluorene CISH10 methyldibenzofuran, isomer Cl3HloO
+
+
+
a a a a a a a b b a b a
b a b b C C
a C C C
a a a a a a b b C
a a b
retention time
name
36 33 min 20 s hexadecane 37 33 min 30 s methyldibenzofuran, isomer
38 33 min 50 s 39 35 min 40 s 40 36 min 16 s 41 36 rnin 26 s 42 37 min 28 s 43 37 min 58 s 44 38 min 42 s 45 39 min 00 s 46 39min 22 s 47 39 min 48 s 48 40 min 30 s 49 41 min 30 s 50 41 min 38 B 51 41 min 54 s 52 42 min 20 s 53 42 rnin 34 s 54 42 min 58 s 55 43 min 40 s 56 44 rnin 10 s 57 44 rnin 50 8 58 46 rnin 34 s 59 46 min 50 s 60 48 min 04 s 61 48 rnin 14 s 62 48 min 22 s 63 48 min 52 s 64 49 rnin 48 s 65 51 rnin 04 s 66 52 min 38 s 67 53 rnin 56 s 68 54 min 50 s 69 55 min 30 s 70 51 rnin 16 s 71 59 rnin 42 s
dibenzyl ether 2-chlorodibenzofuran heptadecane fluorenone phenanthrene 2-chlorofluorene chloromethyldibenzofuran octadecane phytane hydroxyanthracene hydroxyanthracene chlorofluorenone nonadecane methyl palmitate dibutyl phthalate anthraquinone 9-chlorophenanthrene palmitic acid eicosane fluoranthene heneicosane methyl stearate dichlorophenanthrene, isomer stearic acid 9,lO-dichlorophenanthrene docosane 3-chlorofluoranthene tricosane dioctyl adipate tetracosane dichlorofluoranthene, isomer bis(ethylhexy1) phthalate hexacosane heptacosane
formula C16H34
C13H10O C14H140
ClzH70Cl C17H36 C13HS0 C14H10
C13H9C1 ClzHgOCl ClSH38
%OH42 C14H100
identificationa a b a a a a a a C
a a C
C14H100
C
C13H70C1 Cl9HlO
a a a a a a a a a a a b a a a a a a a a a a a
C17H3402
C16H2204 C14HS02
C14H9C1 C16H3202 C20H42 C16H10 C21H44 C1VH3802
Cl4HSCl2 C18H3602 Cl4HSCl2 C22H46
C16H9C1 C23H48 C22H4204
C24H50 C16H8C12 C24H3804 C26H54 C27H56
b
a b
Identification: (a) = comparison with authentic standard; (b) = comparison with library MS; (c) = tentative, based on interpretation of
MS. Environ. Scl. Technol., Vol. 19, No. 7, 1985 587
Table 111. Concentration of PAH and CI-PAH in Tap and Lake Water" n d L ( x ~ O - nmol/L) ~ tap a tap b
tap a
lake
naphthalene (19) dibenzofuran (30) fluorene (34) fluorenone (41) phenanthrene (42) fluoranthene (57) chloronaphthalene (24) chlorodibenzofuran (39) chlorofluorene (43) chlorofluorenone (49) chlorophenanthrene (54) chlorofluoranthene (64) dichloronaphthalene (32)b dichlorophenanthrene (62) dichlorophenanthrene (60)b dichlorofluoranthene (68)b
2.3 (18) 56.2 (335) 3.9 (23) 1.65 (9.2) 0.86 (4.8) 0.02 (0.1) 0.28 (1.7) 1.4 (6.9) 0.13 (0.6) 0.11 (0.5) 0.33 (1.6) 0.13 (0.5) 0.03 (0.2) 0.08 (0.32) 0.03 (0.1) 0.03 (0.1)
0.04 (0.16) 0.02 (0.08) 0.05 (0.18)
0.17 0.15 0.18 0.01 0.10
volume of water, L flow rate, mL/min date
200 57
150 60
200 55
150 60
June 13-16, 1983
Feb 14-17, 1984
May 27-30, 1983
Feb 20-23, 1984
0.31 (2.4) 1.0 (6.0) 0.25 (1.5) 0.28 (1.6) 0.45 (2.5) 0.04 (0.2) 0.03 (0.2) 0.04 (0.2) 0.03 (0.1) 0.04 (0.2) 0.18 (0.8) 0.14 (0.6)
1.03 (8.0) 39.0 (232) 5.8 (35) 7.3 (41) 1.41 (7.9) 0.21 (1.0) 0.44 (2.7) 1.24 (6.1) 0.3 (1.9) 1.22 (5.7)
0.09 (0.7) 0.03 (0.2) 0.04 (0.2)
ND 0.34 (1.9)
NA ND ND ND ND ND ND ND ND ND ND
NA
ND
(0.7) (0.8) (0.7) (0.04) (0.37)
'Compound number refers to Table I1 and Figures 3 and 4. ND, not detected; NA, not analyzed. *Based on relative peak area to the parent PAH (pure standard was not available). Table IV. Molar Ratio of Chlorinated PAH to the Parent PAH' tap a
tap a
tap b
chloronaphthalene (24) chlorodibenzofuran (39) chlorofluorene (43) chlorofluorenone (49) chlorophenanthrene (54) chlorofluoranthene (64) dichloronaphthalene (32)b dichlorophenanthrene (62) dichlorophenanthrene (60)b dichlorofluoranthene
0.10 0.021 0.028 0.056 0.32 6 0.008 0.07 0.03 1.1
0.06 0.03 0.9
0.69 0.09 0.09 0.005 0.35
date
June 13-16, 1983
Feb 14-17, 1984
May 27-30, 1983
0.08 0.03 0.1 0.12 0.34 3
ND
0.34 0.026 0.056 0.14
NA
'Compound number refers to Table I1 and Figures 3 and 4. ND, not detected; NA, not analyzed. bBased on relative peak area to the parent PAH (pure standard was not available). di(ethylhexy1) phthalates, n-alkanes from tetradecane to heptacosane, hexyl ethers, benzyl ether, alkylbenzenes, palmitic and stearic acid, its methyl esters, and PAHs were the major components in every tap water extract. The maximum and minimum concentrations of PAHs, found in four extractions over 1year a t the same location, are the following: naphthalene, 27 and 0.31 ng/L; dibenzofuran 63 and 0.1 ng/L; fluorene, 11.7 and 0.32 ng/L; phenanthrene, 1.3 and 0.44 ng/L; fluoranthene, 0.04 and 0.02 ng/L. Among these, dibenzofuran was the major component in every experiment. Figure 4 shows the mass chromatogram of the seven PAHs (naphthalene, dibenzofuran, fluorene, methyldibenzofuran, fluorenone, phenanthrene, and fluoranthene) and their mono- and dichloro derivatives. Both monochlorinated and dichlorinated derivatives of naphthalene (Figure 4a), phenanthrene (Figure 4d), and fluoranthene (Figure 4e) were found. Only monochlorinated derivatives of dibenzofuran (Figure 4b), fluorene (Figure 4b), methyldibenzofuran (Figure 4c), and fluorenone (Figure 4c) were found, although their parent PAHs were present in fairly large amounts. Some other methylated derivatives such as chloromethylnaphthalene and some other oxygenated PAHs such as anthraquinone and hydroxyanthracene (or phenanthrenol) were also found. In general, reaction of chlorine with model PAHs produces oxygenated and chlorinated derivatives (9-11). Fluorenone, anthra588
Environ. Sci. Technol., Vol. 19, No. 7, 1985
quinone, and phenanthrenol were reported as oxidation products of fluorene, anthracene, and phenanthrene, respectively. Since C1-PAHs were not present in the raw water (Table 111),they should be produced in the tap water supply system by the reaction of the parent PAWS with residual chlorine. The concentrations of PAHs and C1PAHs are shown in Table 111. It was found that the concentrations varied in their order of magnitude. If the reaction of residual chlorine with PAHs remaining in the tap water supply system produces C1-PAHs, the reactivity and contact time of each individual PAH to chlorine determines the ratio of the parent PAH and chlorinated species. The ratio of the concentrations of the chlorinated derivative to the concentration of the parent PAH is shown in Table IV. The ratio in both tap a and tap b water samples decreased in the following order: fluoranthene, phenanthrene, naphthalene, fluorene, and dibenzofuran. From the comparison of the ratio, it was found that the values are similar in two tap a samples but somewhat different between tap a and tap b samples, especially in the ratio of chlorinated fluoranthenes. If two tap samples have the same contamination sources, the ratio must have similar values. Residence times of tap a and tap b water in the distribution system, which can be considered as reaction times in solution phase, were almost the same, so this implies that two tap waters had different contamination sources.
a)
IL.
1
24
1, I
b)
'
,
,
,
x60
43
196
-.
164/ 162
,&
x5 x5
I
19
@@-ClZ
3 2 3 3 x30
128
200
WCi
4I
134
30
202
Other brominated or chlorinated compounds found in the extracts were dichlorobenzenes, chloro- and bromoxylenes, bromoform, bromohexane, hexachloroethane, and bromodecane. Chloroxylene and bromoxylene may be reaction products of xylene which were present in the tap water. Dichlorobenzeneswere also found in the lake water, so they seem to be pollutants in the lake water. Although biphenyl was present at almost the same concentration as fluorene, chlorinated biphenyls were not found in the tap water extracts. This may be due to the lower reactivity of biphenyl to chlorine, compared with PAHs, under the conditions of the tap water supply system.
Conclusion Combination of a modified continuous liquid-liquid extraction and computerized GC/MS using a fused silica capillary column enabled analysis of low concentrations of organic solutes in water. The presence of PAHs and chlorinated PAHs in tap water indicates the reaction of PAHs with chlorine. Acknowledgments N.H.P. is grateful to the Australian Department of Science and Technology for the awarding of a grant under the terms of the Australia-Japan Science and Technology Agreement which enabled him to work at the National Institute for Environmental Studies in Tsukuba, Japan.
e)
68
h
..
A
x3 x3
272, -270
4
CI
Flgure 4. Mass chromatogram of PAHs and chlorinated PAHs in the tap water extract (tap a, 83lJune 13-16, 1983). (Peak numbers refer to Table 11.) (a) Naphthalene ( m l z 128), monochlorinated ( m l z 162, 164), dichlorinated ( m l z 196, 198). (b) Dibenzofuran ( m l z 168), monochlorinated (rn l z 202, 204); fluorene (ml z 166), monochlorinated (mlz 200, 202). (c)Methyldibenzofuran ( m / z 182), monochlorinated ( m l z 216, 218); fluorenone ( m l z l80), monochlorinated ( m / r 214, 216). (d) Phenanthrene ( m l z 178), monochlorinated ( m l r 212, 214), dichlorinated ( m l z 246, 248). (e) Fluoranthene ( m l z 202), monochlorinated ( m l r 236, 238), dichlorinated ( m l z 270, 272).
The fact that dibenzofuran and fluorene were more abundant than the other PAHs in Tsukuba tap water is consistent with that of a chlorination study on coal tar leachate. Alben (1419) reported that on the chlorination of coal tar leachate, oxygen-substituted PAHs such as dibenzofuran became more abundant, several new oxygenated PAHs were formed, and of the parent PAHs, fluorene became the most prominent, with a considerably diminished concentration of phenanthrene and fluoranthene. In Japan, the use of coal tar coated pipes in public water supply systems is permitted. In the lines supplying tap a and tap b, half of the pipes are coated with tar epoxy-resin paints which contain about 70% coal tar. The findings that dibenzofuran and fluorene were abundant and that two taps have different C1-PAH/PAH ratios suggest that the origin of PAHs in Tsukuba tap water is coal tar coated pipes in the water supply system, but further study will be required to differentiate the contamination sources.
Registry No. 1, 100-41-4;3,75-25-2;4,95-47-6;5,9842-8; 6, 111-25-1; 7,103-65-1; 10,106-46-7; 11,25551-13-7; 12,95-50-1; 14, 67-72-1; 16,35884-77-6; 19,91-20-3; 22,112-29-8; 23,112-58-3; 24, 90-13-1; 25,9262-4; 26, 629-59-4; 27, 719-22-2; 30, 132-64-9;31, 629-62-9; 34, 84-65-1; 36, 544-76-3; 38, 103-50-4; 39, 51230-49-0; 40,629-78-7; 41,486-25-9;42,85-01-8;43,2523-44-6;45,593-45-3; 46,638-36-8; 49,85897-29-6;50,629-92-5; 51,112-39-0; 52,84-74-2; 53, 84-65-1; 54,947-72-8; 55,57-10-3; 56, 112-95-8; 57, 206-44-0; 58, 629-94-7; 59, 112-61-8; 60, 59116-88-0; 61, 57-11-4; 62, 17219-94-2;63,629-97-0; 64,25911-51-7;65,638-67-5;66,103-23-1; 67,646-31-1; 68,86329-60-4; 69,117-81-7;70,630-01-3;71,593-49-7; acenaphthylene, 208-96-8; acenaphthene, 83-32-9; anthracene, 120-12-7; chloronaphthalene, 25586-43-0; chlorodibenzofuran, 42934-53-2; chlorofluoranthene,2591 1-51-7;p-xylene, 106-42-3; m-xylene, 108-38-3; ethyltoluene, 25550-14-5; chloroxylene, 25323-41-5; methylbiphenyl, 28652-72-4; methyldibenzofuran, 60826-62-2; dichloronaphthalene, 28699-88-9.
Literature Cited (1) Cheh, A. M.; Skochdopole, J.; Koski, P.; Cole, L. Science (Washington, D.C.) 1980,207, 90-92. (2) Harrison, R. M.; Perry, R.; Wellings, R. A. Enuiron. Sci. Technol. 1976,10, 1151-1156. (3) Oyler, A. R.; Bodenner, D. L.; Welch, K. J.; Liukkonen, R. J.; Carlson, R. M.; Kopperman, H. L.; Caple, R. Anal. Chem. 1978,50,837-842. (4) Oyler, A. R.; Liukkonen, R. J.; Lukasewycz, M. T.; Cox, D. A.; Peake, D. A.; Carlson, R. M. Enuiron. Health Perspect. 1982,46, 73-86. ( 5 ) Oyler, A. R.; Liukkonen, R. J.; Lukasewycz, M. T.;Heikkila, K. E.; Cox, D. A.; Carlson, R. M. Enuiron. Sci. Technol. 1983,17,334-342. (6) Harrison, R. M.; Perry, R.; Wellings, R. A. Water Res. 1975, 9, 331-346. (7) Basu, D. K.; Saxena, J. Enuiron. Sci. Technol. 1978, 12, 795-798. (8) Benoit, F. M.; LeBel, G. L.; Williams, D. T. Bull. Enuiron. Contam. Toxicol. 1979, 23, 774-778. (9) Benoit, F. M.; LeBel, G. Y.; Williams, D. T. Int. J. Enuiron. Anal. Chem. 1979,6, 277-287. (10) Coleman, W. E.; Melton, R. G.; Kopfler, F. C.; Barone, K. A.; Aurand, T. A.; Jellison, M. G. Enuiron. Sci. Technol. 1980,14, 576-588. (11) Kveseth, K.; Sortland, B.; Bokn, T. Chemosphere 1982,11, 623-639. Environ. Sci. Technol., Vol. 19, No. 7, 1985 589
Envlron. Scl. Technol. 1985, 19, 590-596
Grob, K. J . Chromatogr. 1973, 84, 255-273. Ahnoff, M.; Josefsson, B. Anal. Chem. 1974,46,658-663. Ahnoff, M.; Josefsson, B. Anal. Chem. 1976,48,1268-1270. Stachel, B. Baetjer, K.; Cetinkaya, M.; Dueszein, J.; Lahl, U.; Lierse, K.; Thiemann, W.; Gabel, B.; Kozicki, R.; Podbielski, A. Anal. Chem. 1981, 53, 1469-1472. Heller, S. R.; Milne, G. W. A. “EPA/NIH Mass Spectral Data Base”;U.S.Government Printing Offce: Washington,
DC, 1978. (17) Mackay, D.; Shiu, W. Y. J . Chem. Eng. Data 1977, 22, 399-402. (18) Alben, K. Environ. Sci. Technol. 1980, 14, 468-470. (19) Alben, K. Anal. Chem. 1980, 52, 1825-1828. Received for review April 16,1984. Revised manuscript received October 29, 1984. Accepted January 14, 1985.
Henry’s Law Constants for the Polychlorinated Biphenyls Lawrence P. Burkhard,t David E. Armstrong,” and Anders W. Andren
Water Chemistry Program, University of Wisconsin, Madison, Wisconsin 53706 Henry’s law constants were predicted from the ratio of the liquid (or subcooled liquid) vapor pressure and aqueous solubility for each polychlorinated biphenyl (PCB) congener. The liquid vapor pressures and aqueous solubilities were derived for each PCB congener by using correlations of Gibbs’ free energy of vaporization against gas-liquid chromatographic retention indexes and Gibbs’ free energy of solubilization of a liquid against molecular surface area. The predicted values were in fair agreement with experimental values, and the error for these constants was estimated to be a factor of 5 in the temperature range 0.0-40.0 “C. For the PCB congeners, Henry’s law constants were independent of molecular weight and increased approximately an order of magnitude with a 25.0 “C increase in temperature. The average value for Henry’s law constants and air-water partition coefficients for the Aroclor PCB mixtures were approximately 4.0 X atm m3/mol a t 25.0 “C. W
Introduction One of the major problems in modeling and predicting the behavior of polychlorinated biphenyls (PCBs) in the environment has been the lack of accurate Henry’s law constants. Henry’s law constants are used to predict exchange rates of vapors across the air/water interface and fugacity potentials for aqueous systems. In part, Henry’s law constants have not been available due to analytical difficulties in measuring this property. Measurements are often performed with nanomoles or less of the compound. In addition, PCBs were sold commercially as mixtures called Aroclors, and each mixture was composed of numerous, 50-75, PCB congeners ( I ) . Many of these compounds are not readily available in pure form, and thus, much preparatory work is required before any measurements can be performed. Historically, investigators have circumvented this lack of experimental data by treating each Aroclor mixture as a single entity when estimating Henry’s law constants (ITS) (2-6). An average H was determined by dividing the vapor pressure of the mixture by its aqueous solubility (2). The problem with this approach is that PCB congeners behave in the environment as individual compounds and not as a mixture. Consequently, to model their behavior correctly, H’s are needed for each congener. Recently, Bopp (7)) in an attempt to eliminate this problem, grouped PCB congeners by degree of chlorination. The aqueous activity coefficient for each degree of chlorination was assumed to be independent of temperat Present address: Center for Lake Superior Environmental Studies, University of Wisconisin, Superior, WI 55880.
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ture, and the logarithm of the subcooled liquid vapor pressure was considered to be linearly related to chlorine number. These assumptions were used in predicting vapor pressures and solubilities for each degree of chlorination. The predicted values were used to calculate H for each degree of chlorination. Four recent investigations (8-11) now permit calculation of H for each PCB congener and elimination of the assumptions employed by Bopp. These investigations were performed using the best techniques currently available for measuring aqueous solubilities (9, 12) and vapor pressures (13). The requisite data were derived by measurements of vapor pressures of 4 PCB congeners and aqueous solubilities of 18 PCB congeners. These measurements include vapor pressure and solubility data for decachlorobiphenyl,the highest chlorinated PCB congener. The object of this investigation is to use the recently acquired data to calculate and evaluate H for each PCB congener. Temperature effects and the influence of chemical structure on the H s are also considered.
Determination of Henry’s Law Constants Henry’s law expresses the proportionality between the concentration of a gas dissolved in a solvent and its partial pressure (14). In equation form, Henry’s law is P=HC (1) where P is the partial pressure of the gas, C is the concentration of the dissolved gas, and H is Henry’s law constant. Henry’s law represents a limiting behavior for any gas-solvent system as its partial pressure approaches zero. Typically, Henry’s law breaks down when partial pressures exceed 5-10 atm and/or when the dissolved concentrations exceed 3 mol % (24). Henry’s law constant is a function of temperature only for a particular gassolvent system. However, each gas-solvent system has a unique H value. Henry’s law constants are usually determined by measuring the equilibrium partial pressure and dissolved concentration of the gas and then calculating the ratio of these two quantities. For most environmental contaminants, the aqueous solubilities and vapor pressures of the pure substances are very low. Consequently, Henry’s law is valid up to dissolved concentrations equal to the aqueous solubility and to partial pressures equal to the vapor pressure of the pure substance. The validity of Henry’s law at these partial pressures and aqueous concentrations makes it possible to derive the ITS by calculating the ratio of the vapor pressure of the pure compound to its aqueous solubility. We used this method to derive H’s for each PCB congener. The reasons for employing this approach were
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0 1985 American Chemical Society
